Thermally activated calibration system for chemical sensors

Abstract

A device for remotely calibrating leak sensors. A supply of liquid analyte calibrant is stored in a reservoir, and is communicated to an outlet nozzle by a conduit having a throughbore. The conduit terminates in an outlet nozzle, and portion of the conduit defines a dosing chamber for storing a measured dose of the liquid calibrant. A thermal activator such as a resistive coil or a radio frequency unit is disposed adjacent the dosing chamber for applying a steep thermal gradient in order to bring the calibrant quickly to its boiling point such that the measured quantity is ejected from the outlet nozzle.

What is claimed: 
     
       1. A leak sensor calibration device, comprising: a reservoir for storing a liquid calibrant;   a conduit in flow communication with the reservoir, a portion of the conduit defining a dosing chamber for storing a measured quantity of the calibrant;   an outlet nozzle in flow communication with the dosing chamber; and   a thermal activator adjacent the dosing chamber for vaporizing the measured quantity of calibrant in the dosing chamber and ejecting the measured quantity through the outlet nozzle.   
     
     
       2. The device of claim 1, including a remotely operated valve at the outlet nozzle, the valve being shiftable between a closed position wherein the dosing chamber is isolated from the surrounding atmosphere to an open position wherein the dosing chamber is in flow communication with the surrounding atmosphere. 
     
     
       3. The device of claim 1, including a remotely operated valve disposed between the reservoir and the dosing chamber, the valve being shiftable between a closed position wherein the reservoir is isolated from the dosing chamber and an open position wherein the reservoir is in flow communication with the dosing chamber for filling the dosing chamber with the calibrant. 
     
     
       4. The device of claim 1, including first and second remotely operated valves, the first valve being located at the outlet nozzle, the first valve being shiftable between a closed position wherein the dosing chamber is isolated from the surrounding atmosphere to an open position wherein the dosing chamber is in flow communication with the atmosphere, the second valve being disposed between the reservoir and the dosing chamber, the second valve being shiftable between a closed position wherein the reservoir is isolated from the dosing chamber and an open position wherein the reservoir is in flow communication with the dosing chamber. 
     
     
       5. The device of claim 4, wherein the valves are electrically operated, and further including a control system for remotely operating the valves and for energizing the thermal activator. 
     
     
       6. The device of claim 5, wherein the control system maintains the second valve in the closed position and the first valve in the open position when the activator is energized. 
     
     
       7. The device of claim 1, wherein the thermal activator is a resistive coil. 
     
     
       8. The device of claim 1, wherein the thermal activator is a radio frequency unit. 
     
     
       9. The device of claim 1, wherein the thermal activator supplies a thermal gradient sufficient to vaporize the calibrant in the dosing chamber in about 10 milliseconds. 
     
     
       10. A leak sensor calibrating device, comprising: a reservoir for storing a liquid calibrant;   a conduit in flow communication with the storage reservoir, the conduit terminating in an outlet nozzle and having a central portion defining a dosing chamber for storing a measured quantity of the liquid calibrant;   a thermal activator for heating the measured quantity of liquid calibrant in the dosing chamber;   a valve system for isolating the outlet nozzle from the surrounding atmosphere when the thermal activator is inactive and further for isolating the dosing chamber from the reservoir when the thermal activator is active; and   a control system operatively connected to the valve system and the thermal activator.   
     
     
       11. A leak sensor calibration device for injecting a metered quantity of vaporized liquid material in the vicinity of a leak sensor, the device comprising: a reservoir for storing the liquid material;   a conduit in flow communication with the reservoir, a portion of the conduit defining a dosing chamber for storing the metered quantity of the liquid material, the conduit further including an impeding portion for restricting the flow of the liquid material from the dosing chamber back to the reservoir;   an outlet nozzle in flow communication with the dosing chamber; and   a thermal activator adjacent the dosing chamber for vaporizing the liquid material in the dosing chamber thereby ejecting the vaporized material through the outlet nozzle to the atmosphere.   
     
     
       12. The device of claim 11, wherein the impeding portion is a remotely operated valve disposed between the reservoir and the dosing chamber, the valve being shiftable between a closed position wherein the reservoir is isolated from the dosing chamber and an open position wherein the reservoir is in flow communication with the dosing chamber. 
     
     
       13. The device of claim 12, wherein the valve is remotely operable. 
     
     
       14. The device of claim 11, including a remotely operated outlet valve at the outlet nozzle, the valve being shiftable between a closed position wherein the dosing chamber is isolated from the surrounding atmosphere to an open position wherein the dosing chamber is in flow communication with the surrounding atmosphere. 
     
     
       15. The device of claim 11, including an first valve at the outlet nozzle and wherein the impeding portion includes a second valve, each of the valves being remotely operable, the first valve being shiftable between a closed position wherein the dosing chamber is isolated from the surrounding atmosphere to an open position wherein the dosing chamber is in flow communication with the atmosphere, the second valve being disposed between the reservoir and the dosing chamber, the second valve being shiftable between a closed position wherein the reservoir is isolated from the dosing chamber and an open position wherein the reservoir is in flow communication with the dosing chamber. 
     
     
       16. The device of claim 15, wherein the valves are electrically operated, and further including a control system for controlling the valves and for energizing the thermal activator. 
     
     
       17. The device of claim 16, wherein the control system maintains the second valve in the closed position and the first valve in the open position when the activator is energized. 
     
     
       18. The device of claim 11, wherein the elevation of the outlet is disposed above the elevation of the impeding portion. 
     
     
       19. The device of claim 11, wherein the pneumatic impedance through the impeding portion is about fifty times greater than the pneumatic impedance through the outlet nozzle. 
     
     
       20. The device of claim 11, wherein the volume of the dosing chamber is about 2×10 -6  liters.